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Date: Wed, 18 Jun 2014 10:18:50 -0400
From: Boris Ostrovsky <boris.ostrovsky@...cle.com>
To: Wei Liu <wei.liu2@...rix.com>
CC: xen-devel@...ts.xen.org, netdev@...r.kernel.org,
Ian Campbell <ian.campbell@...rix.com>,
David Vrabel <david.vrabel@...rix.com>
Subject: Re: [PATCH net] xen-netback: bookkeep number of queues in our own
module
On 06/18/2014 10:09 AM, Wei Liu wrote:
> The original code uses netdev->real_num_tx_queues to bookkeep number of
> queues and invokes netif_set_real_num_tx_queues to set the number of
> queues. However, netif_set_real_num_tx_queues doesn't allow
> real_num_tx_queues to be smaller than 1, which means setting the number
> to 0 will not work and real_num_tx_queues is untouched.
>
> This is bogus when xenvif_free is invoked before any number of queues is
> allocated. That function needs to iterate through all queues to free
> resources. Using the wrong number of queues results in NULL pointer
> dereference.
>
> So we bookkeep the number of queues in xen-netback to solve this
> problem. The usage of real_num_tx_queues in core driver is to cap queue
> index to a valid value. In start_xmit we've already guarded against out
> of range queue index so we should be fine.
>
> This fixes a regression introduced by multiqueue patchset in 3.16-rc1.
David sent a couple of patches earlier today that I have been testing
and they appear to fix both netfront and netback. (I am waiting for
32-bit to finish)
http://lists.xenproject.org/archives/html/xen-devel/2014-06/msg02308.html
-boris
>
> Reported-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Signed-off-by: Wei Liu <wei.liu2@...rix.com>
> CC: Ian Campbell <ian.campbell@...rix.com>
> ---
> drivers/net/xen-netback/common.h | 1 +
> drivers/net/xen-netback/interface.c | 30 +++++++++++++-----------------
> drivers/net/xen-netback/xenbus.c | 20 ++++++--------------
> 3 files changed, 20 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
> index 4dd7c4a..93602a6 100644
> --- a/drivers/net/xen-netback/common.h
> +++ b/drivers/net/xen-netback/common.h
> @@ -222,6 +222,7 @@ struct xenvif {
>
> /* Queues */
> struct xenvif_queue *queues;
> + unsigned int num_queues;
>
> /* Miscellaneous private stuff. */
> struct net_device *dev;
> diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
> index 852da34..7daf64c 100644
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -140,7 +140,8 @@ static void xenvif_wake_queue_callback(unsigned long data)
> static u16 xenvif_select_queue(struct net_device *dev, struct sk_buff *skb,
> void *accel_priv, select_queue_fallback_t fallback)
> {
> - unsigned int num_queues = dev->real_num_tx_queues;
> + struct xenvif *vif = netdev_priv(dev);
> + unsigned int num_queues = vif->num_queues;
> u32 hash;
> u16 queue_index;
>
> @@ -162,7 +163,7 @@ static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
> {
> struct xenvif *vif = netdev_priv(dev);
> struct xenvif_queue *queue = NULL;
> - unsigned int num_queues = dev->real_num_tx_queues;
> + unsigned int num_queues = vif->num_queues;
> u16 index;
> int min_slots_needed;
>
> @@ -225,7 +226,7 @@ static struct net_device_stats *xenvif_get_stats(struct net_device *dev)
> {
> struct xenvif *vif = netdev_priv(dev);
> struct xenvif_queue *queue = NULL;
> - unsigned int num_queues = dev->real_num_tx_queues;
> + unsigned int num_queues = vif->num_queues;
> unsigned long rx_bytes = 0;
> unsigned long rx_packets = 0;
> unsigned long tx_bytes = 0;
> @@ -256,7 +257,7 @@ out:
> static void xenvif_up(struct xenvif *vif)
> {
> struct xenvif_queue *queue = NULL;
> - unsigned int num_queues = vif->dev->real_num_tx_queues;
> + unsigned int num_queues = vif->num_queues;
> unsigned int queue_index;
>
> for (queue_index = 0; queue_index < num_queues; ++queue_index) {
> @@ -272,7 +273,7 @@ static void xenvif_up(struct xenvif *vif)
> static void xenvif_down(struct xenvif *vif)
> {
> struct xenvif_queue *queue = NULL;
> - unsigned int num_queues = vif->dev->real_num_tx_queues;
> + unsigned int num_queues = vif->num_queues;
> unsigned int queue_index;
>
> for (queue_index = 0; queue_index < num_queues; ++queue_index) {
> @@ -379,7 +380,7 @@ static void xenvif_get_ethtool_stats(struct net_device *dev,
> struct ethtool_stats *stats, u64 * data)
> {
> struct xenvif *vif = netdev_priv(dev);
> - unsigned int num_queues = dev->real_num_tx_queues;
> + unsigned int num_queues = vif->num_queues;
> int i;
> unsigned int queue_index;
> struct xenvif_stats *vif_stats;
> @@ -436,10 +437,7 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
> char name[IFNAMSIZ] = {};
>
> snprintf(name, IFNAMSIZ - 1, "vif%u.%u", domid, handle);
> - /* Allocate a netdev with the max. supported number of queues.
> - * When the guest selects the desired number, it will be updated
> - * via netif_set_real_num_tx_queues().
> - */
> + /* Allocate a netdev with the max. supported number of queues. */
> dev = alloc_netdev_mq(sizeof(struct xenvif), name, ether_setup,
> xenvif_max_queues);
> if (dev == NULL) {
> @@ -458,11 +456,9 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
> vif->dev = dev;
> vif->disabled = false;
>
> - /* Start out with no queues. The call below does not require
> - * rtnl_lock() as it happens before register_netdev().
> - */
> + /* Start out with no queues. */
> vif->queues = NULL;
> - netif_set_real_num_tx_queues(dev, 0);
> + vif->num_queues = 0;
>
> dev->netdev_ops = &xenvif_netdev_ops;
> dev->hw_features = NETIF_F_SG |
> @@ -677,7 +673,7 @@ static void xenvif_wait_unmap_timeout(struct xenvif_queue *queue,
> void xenvif_disconnect(struct xenvif *vif)
> {
> struct xenvif_queue *queue = NULL;
> - unsigned int num_queues = vif->dev->real_num_tx_queues;
> + unsigned int num_queues = vif->num_queues;
> unsigned int queue_index;
>
> if (netif_carrier_ok(vif->dev))
> @@ -724,7 +720,7 @@ void xenvif_deinit_queue(struct xenvif_queue *queue)
> void xenvif_free(struct xenvif *vif)
> {
> struct xenvif_queue *queue = NULL;
> - unsigned int num_queues = vif->dev->real_num_tx_queues;
> + unsigned int num_queues = vif->num_queues;
> unsigned int queue_index;
> /* Here we want to avoid timeout messages if an skb can be legitimately
> * stuck somewhere else. Realistically this could be an another vif's
> @@ -751,9 +747,9 @@ void xenvif_free(struct xenvif *vif)
> /* Free the array of queues. The call below does not require
> * rtnl_lock() because it happens after unregister_netdev().
> */
> - netif_set_real_num_tx_queues(vif->dev, 0);
> vfree(vif->queues);
> vif->queues = NULL;
> + vif->num_queues = 0;
>
> free_netdev(vif->dev);
>
> diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
> index 96c63dc2..c724538 100644
> --- a/drivers/net/xen-netback/xenbus.c
> +++ b/drivers/net/xen-netback/xenbus.c
> @@ -527,9 +527,7 @@ static void connect(struct backend_info *be)
> /* Use the number of queues requested by the frontend */
> be->vif->queues = vzalloc(requested_num_queues *
> sizeof(struct xenvif_queue));
> - rtnl_lock();
> - netif_set_real_num_tx_queues(be->vif->dev, requested_num_queues);
> - rtnl_unlock();
> + be->vif->num_queues = requested_num_queues;
>
> for (queue_index = 0; queue_index < requested_num_queues; ++queue_index) {
> queue = &be->vif->queues[queue_index];
> @@ -546,9 +544,7 @@ static void connect(struct backend_info *be)
> * earlier queues can be destroyed using the regular
> * disconnect logic.
> */
> - rtnl_lock();
> - netif_set_real_num_tx_queues(be->vif->dev, queue_index);
> - rtnl_unlock();
> + be->vif->num_queues = queue_index;
> goto err;
> }
>
> @@ -561,9 +557,7 @@ static void connect(struct backend_info *be)
> * and also clean up any previously initialised queues.
> */
> xenvif_deinit_queue(queue);
> - rtnl_lock();
> - netif_set_real_num_tx_queues(be->vif->dev, queue_index);
> - rtnl_unlock();
> + be->vif->num_queues = queue_index;
> goto err;
> }
> }
> @@ -582,13 +576,11 @@ static void connect(struct backend_info *be)
> return;
>
> err:
> - if (be->vif->dev->real_num_tx_queues > 0)
> + if (be->vif->num_queues > 0)
> xenvif_disconnect(be->vif); /* Clean up existing queues */
> vfree(be->vif->queues);
> be->vif->queues = NULL;
> - rtnl_lock();
> - netif_set_real_num_tx_queues(be->vif->dev, 0);
> - rtnl_unlock();
> + be->vif->num_queues = 0;
> return;
> }
>
> @@ -596,7 +588,7 @@ err:
> static int connect_rings(struct backend_info *be, struct xenvif_queue *queue)
> {
> struct xenbus_device *dev = be->dev;
> - unsigned int num_queues = queue->vif->dev->real_num_tx_queues;
> + unsigned int num_queues = queue->vif->num_queues;
> unsigned long tx_ring_ref, rx_ring_ref;
> unsigned int tx_evtchn, rx_evtchn;
> int err;
--
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